Six Sigma management and grey relational analysis to improve performance of tableting process

This research implements the well-known Six Sigma approach define-measure-analyse improve-control (DMAIC) to improve the performance of direct compression process with two quality responses: tablet's weight and hardness. At define phase, the x-bar and s charts are established and judged in-control for both responses. To measure performance, the values of the actual capability indices for hardness and weight are estimated 1.5 and 0.587, respectively, which indicate that the tableting process is capable for tablet's hardness but it is incapable for weight. At the analyse and improve phases, designed experiments utilising the Taguchi's L27 array followed by the grey relational analysis (GRA) technique are implemented to determine the combination of factor levels that enhance process performance. After process improvement, the capability index values are found equal to 3.31 and 0.848. To control performance, the value of the multivariate capability index is found equal to 0.938 at initial factor settings, while it is enhanced using optimal factor settings to 1.68. Finally, the multivariate control charts for Hotelling T² and generalised variance are employed to monitor future production. In conclusion, the DMAIC approach including GRA techniques is found effective for improving the performance of direct compression with tablet's weight and hardness.